1. Field of the Invention
The present invention relates to an apparatus and method for introducing sealant into a clearance between a replacement pipe and an existing pipe within which, in use, the replacement pipe is located.
2. Discussion of the Background
UK Published Patent Application Nos. 2227071A and 2236158A both describe methods for replacing or relining pipes, particularly domestic gas service pipes, with replacement pipes.
In the methods described, after the replacement pipe has been inserted into the existing pipe, any clearance between the pipes is sealed with a sealant of a flowable, settable kind such as grout or an anaerobic sealant or any other suitable kind of sealant.
The sealant is injected into the downstream end of the clearance via a suitable fitting, it being understood that the terms "downstream" and "upstream" are used in relation to the normal direction of flow of gas in the existing service pipe from the main towards and into the premises. The injected sealant travels upstream along the clearance until it reaches the so-called "nose-cone". This is a component which is connected to the leading end of the replacement pipe before it is inserted into the existing service pipe. The nose-cone has a tubular body with a downstream portion connected to the upstream/leading end of the replacement pipe. Around the upstream portion of the body usually are means for sealing the clearance between the pipes when the replacement pipe is located within the existing pipe. The sealing means in the nose-cone are in the form of a flange or flanges or a vane or vanes and form a tight interference fit with the internal wall of the existing pipe. It is these flanges or vanes which stop gas from entering the clearance and also prevent the further progress of the sealant during its journey along the clearance. The nose-cone also has a frangible means to seal the bore of the tubular nose-cone body. This serves temporarily to prevent the ingress of gas into the replacement pipe.
When the sealant reaches the nose-cone, it is a signal that the entire clearance is occupied by sealant and that the clearance is completely sealed, the seal provided by the flange(s) or vane(s) not being considered totally secure.
The distance between the downstream injection point in the clearance and the nose-cone may be several meters as the distance will be equivalent to the length of service pipe being replaced. Clearly to fill the entire clearance a very large quantity of sealant is necessary and this increases the costs of these particular replacement methods.